Waste disposal for 3d printing

ABSTRACT

Additive manufacturing or 3D printing produces considerable quantities of waste ink or resin during the course of additive manufacture. The waste ink is a hazardous substance and must be collected and disposed of accordingly. The present embodiments provide a waste ink collection device that collects the waste ink from the printing process, or from head cleaning and other incidental operations, stores the waste and cures it. The waste ink is thus rendered safe for conventional disposal. A waste ink disposal cartridge collects the waste ink and carries out curing.

RELATED APPLICATIONS

This application is Continuation of U.S. patent application Ser. No.15/744,087, filed on on Jan. 12, 2018, which is a National Phase of PCTPatent Application No. PCT/IL2016/050754 having International FilingDate of Jul. 13, 2016, which claims the benefit of priority under 35 USC§ 119(e) of U.S. Provisional Patent Application No. 62/191,687 filed onJul. 13, 2015. The contents of the above applications are allincorporated by reference as if fully set forth herein in theirentirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to a methodand apparatus for waste disposal in 3D printing or additive manufactureand, more particularly, but not exclusively, to a method of wastedisposal which is environmentally safe.

3D printing, otherwise known as additive manufacture, is a technologywhich has been developed and improved over the last two decades and isnow practical and useful for industrial applications. 3D printing buildsunit objects from the bottom-up by adding material layer-by-layer, andis thus able to form uniquely individual parts with incomparably complexshapes.

3D printing is carried out using special inks or resins which are jettedusing nozzles when in liquid form to form a layer, then the layer isrolled with a roller to form a smooth shape, and following rolling thelayer is cured using LED light to solidify the ink.

The roller generates a significant amount of waste, being some 10-30% ofthe volume of ink in the original jetting operation. Additional inkwaste is generated by head maintenance procedures such as purging theheads and spitting out residue inks. The liquid waste resin isconsidered a hazardous substance and requires to be stored and disposedof properly. Needless to say, removing some 30% of the ink in liquidform after use is a considerable overhead in printer operation andenvironmentally friendly disposal is costly.

Currently, the waste is collected and pumped into a disposable containerwhich, when full is shipped to a disposal facility. The facility treatsthe waste and disposes of it in the appropriate manner.

SUMMARY OF THE INVENTION

The present embodiments aim to solve the problems of the prior art byremoving the need for safe disposal of unused liquid resins.

The unused liquid resins are automatically collected and may be cured.The cured ink is no longer a hazardous material and standard disposalcan be used. Curing may be carried out during collection, that isimmediately following the generation of the waste, and the presentembodiments may provide that at no time is there any significant storeof hazardous waste.

According to an aspect of some embodiments of the present inventionthere is provided additive manufacturing apparatus producing waste inkduring the course of additive manufacture, the apparatus comprising:

a waste ink collection device configured to collect waste ink from theadditive manufacturing location; and

a waste ink curing device configured to cure the waste ink uponcollection.

In an embodiment, the waste ink curing device comprises:

a collecting cartridge to collect the waste ink in liquid form; and

a curing energy source to cure the waste ink.

In an embodiment, the waste ink curing device further comprises a switchto operate the curing energy source when the ink is evenly distributedin the cartridge.

In an embodiment, the switch is configured to delay the operating thecuring energy source to allow time for droplets of the waste ink droppedinto the cartridge to merge.

In an embodiment, the waste ink collecting device comprises:

a reservoir for collecting the waste ink from a roller or from printinghead servicing; and

a tubing system for distributing the waste ink to drip pointsdistributed evenly over a collecting cartridge.

In an embodiment, the waste ink collecting cartridge comprises an arrayof distributed drip points for even distribution of the waste ink overthe waste collecting cartridge.

In an embodiment, the curing energy source is located to radiate energyevenly over the cartridge.

In an embodiment, the curing energy source comprises a bank or a stripof light emitting diodes, typically UV light emitting diodes.

In an embodiment, the curing energy source is located lengthwise alongthe cartridge towards one side.

In an embodiment, the drip points comprise shielding against curingenergy from the source, to protect waste ink from being cured prior todripping from the drip points.

In an embodiment, the shielding comprises hoods surrounding each drippoint.

An embodiment may comprise a dispensing shovel below each drip point todirect dripping.

In an embodiment, the curing energy source comprises three banks ofdiodes, a first located lengthwise on a first side of the cartridge, asecond located lengthwise on a second side of the cartridge and a thirdlocated lengthwise above the exit points, the third bank configured forsingle operation upon the cartridge reaching a full state to cureundripped ink.

In an embodiment, the cartridge comprises a level detector to detect acurrent level of waste ink in the cartridge, thereby to determine whenthe cartridge is full.

In an embodiment, the level detector comprises a prism having an indexof refraction selected to cause total internal reflection except whensurrounded by the waste ink.

In an embodiment, the curing energy source comprises first and secondbanks of diodes each directed at an oblique angle towards a floor of thecartridge.

According to a second aspect of the present invention there is provideda method for waste ink management during additive manufacturingcomprising:

delivering ink to an additive manufacturing location;

collecting waste ink from the additive manufacturing location; and

curing the waste ink upon collection.

The method may comprise:

monitoring a waste ink flow rate; and

operating the curing in accordance with the waste ink flow rate.

In an embodiment, the waste ink curing comprises:

collecting the waste ink in liquid form; and

curing the waste ink with curing energy.

The method may operate the curing energy source after allowing for theink to be evenly distributed in the cartridge.

The method may comprise delaying the operating the curing energy sourceto allow time for droplets of the waste ink dropped into the cartridgeto merge.

In an embodiment, the waste ink collecting comprises:

collecting the waste ink from a roller or from printing head servicing;and

distributing the waste ink evenly over a collecting cartridge.

The method may comprise radiating curing energy evenly over thecartridge.

The method may comprise:

detecting when the cartridge is full; and

irradiating drip pipes of the cartridge to cure undripped ink.

According to a third aspect of the present invention there is provided acartridge for receiving waste ink from an additive manufacturing device;the cartridge comprising a distribution head, a curing source and acontainer, wherein the distribution head comprises an inlet pipe and anarray of drip points distributed over the cartridge, wherein the drippoints are respectively surrounded shielding to protect from directirradiation from the curing source; and the curing source comprises aplurality of radiation locations arranged around the container.

The drip points may comprise sharp terminations for droplet formation.

The cartridge may comprise drip-directing shovels below each of the drippoints and within the shielding.

The cartridge may comprise a second curing source within thedistribution head for curing ink remaining in the distribution head whenthe cartridge is full.

The cartridge may comprise a level detector to detect filling of thecartridge. The

level detector may use an LED, a detector and simple reflection, or aprism, as discussed herein.

According to a third aspect of the present invention there is provided amethod of controlling curing in an additive manufacturing apparatusproducing waste ink during the course of additive manufacture, theapparatus comprising:

a waste ink collection device configured to collect waste ink from theadditive manufacturing location; and

a waste ink curing device configured to cure said waste ink uponcollection, the method comprising:

estimating a resin flow to said waste ink collection device;

using said estimate to calculate timing and quantity of resin arrivingat said waste ink collection device; and

operating said curing at a timing and dosage suitable for saidcalculated quantity.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIGS. 1A, 1B, 1C and 1D are schematic illustrations of an additivemanufacturing system according to some embodiments of the invention;

FIGS. 2A, 2B and 2C are schematic illustrations of printing headsaccording to some embodiments of the present invention;

FIGS. 3A, 3B, 3C, 3D, 3E and 3F are schematic illustrationsdemonstrating coordinate transformations according to some embodimentsof the present invention;

FIG. 4 is a simplified diagram showing an additive manufacturingapparatus with waste collection according to an embodiment of thepresent invention;

FIG. 5 is a simplified schematic diagram showing the path of waste inkor resin from the printing location to the collection cartridgeaccording to an embodiment of the present invention;

FIG. 6 is a simplified schematic diagram showing a head part of acartridge assembly according to an embodiment of the present invention;

FIGS. 7 and 8 are photographs of a collection cartridge according to anembodiment of the present invention in which waste ink is shown in twodifferent stages of coalescing;

FIG. 9 is a simplified diagram showing a side cutaway view of a wasteink collecting cartridge according to an embodiment of the presentinvention and illustrating the locations for curing LEDs;

FIG. 10 illustrates a construction and location for dripping points in ashower head of a collecting cartridge according to an embodiment of thepresent invention;

FIG. 11 is a simplified diagram showing a cutaway view of drip exitpoints in a showerhead according to an embodiment of the presentinvention;

FIGS. 12A, 12B and 12C are three cutaway views of a waste ink collectingcartridge according to an embodiment of the present invention;

FIGS. 13A and 13B are two side sections of a level detector for acollecting cartridge according to an embodiment of the presentinvention;

FIG. 14 is an alternative embodiment of a level detector for acollecting cartridge according to the present invention;

FIG. 15 is a flow chart showing operation of the collecting and curingprocess for waste ink according to an embodiment of the presentinvention;

FIG. 16 is a simplified flow chart showing monitoring of waste ink flowrate and using of the result to control the curing rate or dosage,according to an embodiment of the present invention;

FIG. 17 is a photograph illustrating various stages of buildup of resinor ink in the collecting cartridge during operation of the presentinvention;

FIG. 18 is a photograph illustrating layering structure in the curedwaste resin;

FIG. 19 is a photograph illustrating buildup of stalagmites;

FIG. 20 is a photograph illustrating uncured pockets of liquid resinwithin the generally cured mass;

FIGS. 21A, 21B and 21C are photographs illustrating how buildup ofstalagmites causes pockets of liquid resin to form in the resultingshadows; and

FIG. 22 is a photograph showing LED locations and using triangles toshow how curing light covers the interior of the cartridge withillumination from at least two points according to an embodiment of thepresent invention;

FIG. 23 is a simplified diagram illustrating a waste disposal system fora 3D printer according to a further embodiment of the present invention;

FIG. 24 is an exploded diagram of the system of FIG. 23;

FIG. 25 is a simplified diagram showing a waste director component ofthe system of FIG. 23;

FIG. 26A shows a shower head component of the system of FIG. 23;

FIG. 26B is a detail of a part of the component of FIG. 26A;

FIGS. 27, 28 and 29 are different perspective views of structure withinthe waste director component of FIG. 25;

FIG. 30 is a simplified side view of the waste director component ofFIG. 25;

FIG. 31 is a simplified side view of the waste director component ofFIG. 25 fitted onto the shower head component of FIG. 26A;

FIGS. 32, 33 and 34 are simplified diagrams showing protectionstructures for protecting drip openings of the system of FIG. 23 frominadvertent curing;

FIG. 35 illustrates stalactite formation from insufficiently protecteddrip openings;

FIG. 36 illustrates LED and drip hole interrelationships to ensureuniform curing according to embodiments of the present invention; and

FIG. 37 illustrates a virtual waste pipeline model for predicting resinflows in order to calculate correct timing and dosage of curingaccording to an embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to disposalof waste ink or resin during additive manufacture, and, moreparticularly, but not exclusively, to a way of enabling standard wastedisposal to be safely used.

Unused resin is a hazardous material and must be disposed of usingspecial waste disposal techniques, which typically become theresponsibility of the resin provider. The 3D printing process generatesa significant amount of waste, typically some ˜10-30% of the volumejetted by the heads. Additional waste is also generated by headmaintenance procedures such as purging and spitting.

While waste resin in liquid form is considered hazardous, cured resin isnot hazardous and can be disposed of in the regular trash. The presentembodiments thus cure the waste resin as it is generated. Once the wasteresin cartridge is full the user simply throws the cartridge in thetrash and replaces it with a new one.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings and/or the Examples. The invention iscapable of other embodiments or of being practiced or carried out invarious ways.

The method and system of the present embodiments manufacturethree-dimensional objects based on computer object data in a layerwisemanner by forming a plurality of layers in a configured patterncorresponding to the shape of the objects. The computer object data canbe in any known format, including, without limitation, a StandardTessellation Language (STL) or a StereoLithography Contour (SLC) format,Virtual Reality Modeling Language (VRML), Additive Manufacturing File(AMF) format, Drawing Exchange Format (DXF), Polygon File Format (PLY)or any other format suitable for Computer-Aided Design (CAD).

The term “object” as used herein refers to a whole object or a partthereof.

Each layer is formed by an additive manufacturing apparatus which scansa two-dimensional surface and patterns it. While scanning, the apparatusvisits a plurality of target locations on the two-dimensional layer orsurface, and decides, for each target location or a group of targetlocations, whether or not the target location or group of targetlocations is to be occupied by building material, and which type ofbuilding material is to be delivered thereto. The decision is madeaccording to a computer image of the surface.

In preferred embodiments of the present invention the AM comprisesthree-dimensional printing, more preferably three-dimensional inkjetprinting. In these embodiments a building material is dispensed from adispensing head having a set of nozzles to deposit building material inlayers on a supporting structure. The AM apparatus thus dispensesbuilding material in target locations which are to be occupied andleaves other target locations void. The apparatus typically includes aplurality of dispensing heads, each of which can be configured todispense a different building material. Thus, different target locationscan be occupied by different building materials. The types of buildingmaterials can be categorized into two major categories: modelingmaterial and support material. The support material serves as asupporting matrix or construction for supporting the object or objectparts during the fabrication process and/or other purposes, e.g.,providing hollow or porous objects. Support constructions mayadditionally include modeling material elements, e.g. for furthersupport strength.

The modeling material is generally a composition which is formulated foruse in additive manufacturing and which is able to form athree-dimensional object on its own, i.e., without having to be mixed orcombined with any other substance.

The final three-dimensional object is made of the modeling material or acombination of modeling materials or modeling and support materials ormodification thereof (e.g., following curing). All these operations arewell-known to those skilled in the art of solid freeform fabrication.

In some exemplary embodiments of the invention an object is manufacturedby dispensing two or more different modeling materials, each materialfrom a different dispensing head of the AM. The materials are optionallyand preferably deposited in layers during the same pass of the printingheads. The materials and combination of materials within the layer areselected according to the desired properties of the object. Arepresentative and non-limiting example of a system 110 suitable for AMof an object 112 according to some embodiments of the present inventionis illustrated in FIG. 1A. System 110 comprises an additivemanufacturing apparatus 114 having a dispensing unit 16 which comprisesa plurality of dispensing heads. Each head preferably comprises an arrayof one or more nozzles 122, as illustrated in FIGS. 2A-2C describedbelow, through which a liquid building material 124 is dispensed.

Preferably, but not obligatorily, apparatus 114 is a three-dimensionalprinting apparatus, in which case the dispensing heads are printingheads, and the building material is dispensed via inkjet technology.This need not necessarily be the case, since, for some applications, itmay not be necessary for the additive manufacturing apparatus to employthree-dimensional printing techniques. Representative examples ofadditive manufacturing apparatus contemplated according to variousexemplary embodiments of the present invention include, withoutlimitation, fused deposition modeling apparatus and fused materialdeposition apparatus.

Each dispensing head is optionally and preferably fed via a buildingmaterial reservoir which may optionally include a temperature controlunit (e.g., a temperature sensor and/or a heating device), and amaterial level sensor. To dispense the building material, a voltagesignal is applied to the dispensing heads to selectively depositdroplets of material via the dispensing head nozzles, for example, as inpiezoelectric inkjet printing technology. The dispensing rate of eachhead depends on the number of nozzles, the type of nozzles and theapplied voltage signal rate (frequency). Such dispensing heads are knownto those skilled in the art of solid freeform fabrication.

Preferably, but not obligatorily, the overall number of dispensingnozzles or nozzle arrays is selected such that half of the dispensingnozzles are designated to dispense support material and half of thedispensing nozzles are designated to dispense modeling material, i.e.the number of nozzles jetting modeling materials is the same as thenumber of nozzles jetting support material. In the representativeexample of FIG. 1A, four dispensing heads 16 a, 16 b, 16 c and 16 d areillustrated. Each of heads 16 a, 16 b, 16 c and 16 d has a nozzle array.In this Example, heads 16 a and 16 b can be designated for modelingmaterial/s and heads 16 c and 16 d can be designated for supportmaterial. Thus, head 16 a can dispense a first modeling material, head16 b can dispense a second modeling material and heads 16 c and 16 d canboth dispense support material. In an alternative embodiment, heads 16 cand 16 d, for example, may be combined in a single head having twonozzle arrays for depositing support material.

Yet it is to be understood that it is not intended to limit the scope ofthe present invention and that the number of modeling materialdepositing heads (modeling heads) and the number of support materialdepositing heads (support heads) may differ.

Generally, the number of modeling heads, the number of support heads andthe number of nozzles in each respective head or head array are selectedsuch as to provide a predetermined ratio, a, between the maximaldispensing rate of the support material and the maximal dispensing rateof modeling material. The value of the predetermined ratio, a, ispreferably selected to ensure that in each formed layer, the height ofmodeling material equals the height of support material. Typical valuesfor a are from about 0.6 to about 1.5.

As used herein the term “about” refers to ±10%.

For example, for a=1, the overall dispensing rate of support material isgenerally the same as the overall dispensing rate of the modelingmaterial when all modeling heads and support heads operate.

In a preferred embodiment, there are M modeling heads each having marrays of p nozzles, and S support heads each having s arrays of qnozzles such that M×m×p=S×s×q. Each of the M×m modeling arrays and S×ssupport arrays can be manufactured as a separate physical unit, whichcan be assembled and disassembled from the group of arrays. In thisembodiment, each such array optionally and preferably comprises atemperature control unit and a material level sensor of its own, andreceives an individually controlled voltage for its operation.

Apparatus 114 can further comprise a hardening device 324 which caninclude any device configured to emit light, heat or the like that maycause the deposited material to hardened. For example, hardening device324 can comprise one or more radiation sources, which can be, forexample, an ultraviolet or visible or infrared lamp, or other sources ofelectromagnetic radiation, or electron beam source, depending on themodeling material being used. In some embodiments of the presentinvention, hardening device 324 serves for curing or solidifying themodeling material.

The dispensing head and radiation source are preferably mounted in aframe or block 128 which is preferably operative to reciprocally moveover a tray 360, which serves as the working surface. In someembodiments of the present invention the radiation sources are mountedin the block such that they follow in the wake of the dispensing headsto at least partially cure or solidify the materials just dispensed bythe dispensing heads. Tray 360 is positioned horizontally. According tothe common conventions an X-Y-Z Cartesian coordinate system is selectedsuch that the X-Y plane is parallel to tray 360. Tray 360 is preferablyconfigured to move vertically (along the Z direction), typicallydownward. In various exemplary embodiments of the invention, apparatus114 further comprises one or more leveling devices 132, e.g. a roller326. Leveling device 326 serves to straighten, level and/or establish athickness of the newly formed layer prior to the formation of thesuccessive layer thereon. Leveling device 326 preferably comprises awaste collection device 136 for collecting the excess material generatedduring leveling. Waste collection device 136 may comprise any mechanismthat delivers the material to a waste tank or waste cartridge. The wastecollection is discussed in greater detail hereinbelow.

In use, the dispensing heads of unit 16 move in a scanning direction,which is referred to herein as the X direction, and selectively dispensebuilding material in a predetermined configuration in the course oftheir passage over tray 360. The building material typically comprisesone or more types of support material and one or more types of modelingmaterial. The passage of the dispensing heads of unit 16 is followed bythe curing of the modeling material(s) by radiation source 126. In thereverse passage of the heads, back to their starting point for the layerjust deposited, an additional dispensing of building material may becarried out, according to predetermined configuration. In the forwardand/or reverse passages of the dispensing heads, the layer thus formedmay be straightened by leveling device 326, which preferably follows thepath of the dispensing heads in their forward and/or reverse movement.Once the dispensing heads return to their starting point along the Xdirection, they may move to another position along an indexingdirection, referred to herein as the Y direction, and continue to buildthe same layer by reciprocal movement along the X direction.Alternately, the dispensing heads may move in the Y direction betweenforward and reverse movements or after more than one forward-reversemovement. The series of scans performed by the dispensing heads tocomplete a single layer is referred to herein as a single scan cycle.

Once the layer is completed, tray 360 is lowered in the Z direction to apredetermined Z level, according to the desired thickness of the layersubsequently to be printed. The procedure is repeated to formthree-dimensional object 112 in a layerwise manner.

In another embodiment, tray 360 may be displaced in the Z directionbetween forward and reverse passages of the dispensing head of unit 16,within the layer. Such Z displacement is carried out in order to causecontact of the leveling device with the surface in one direction andprevent contact in the other direction.

System 110 optionally and preferably comprises a building materialsupply system 330 which comprises the building material containers orcartridges and supplies a plurality of building materials to fabricationapparatus 114. A control unit 340 controls fabrication apparatus 114 andoptionally and preferably also supply system 330. Control unit 340typically includes an electronic circuit configured to perform thecontrolling operations. Control unit 340 preferably communicates with adata processor 154 which transmits digital data pertaining tofabrication instructions based on computer object data, e.g., a CADconfiguration represented on a computer readable medium in a form of aStandard Tessellation

Language (STL) format or the like. Typically, control unit 340 controlsthe voltage applied to each dispensing head or nozzle array and thetemperature of the building material in the respective printing head.

Once the manufacturing data is loaded to control unit 340 it can operatewithout user intervention. In some embodiments, control unit 340receives additional input from the operator, e.g., using data processor154 or using a user interface 116 communicating with unit 340. Userinterface 116 can be of any type known in the art, such as, but notlimited to, a keyboard, a touch screen and the like. For example,control unit 340 can receive, as additional input, one or more buildingmaterial types and/or attributes, such as, but not limited to, color,characteristic distortion and/or transition temperature, viscosity,electrical property, magnetic property. Other attributes and groups ofattributes are also contemplated.

Another representative and non-limiting example of a system 10 suitablefor AM of an object according to some embodiments of the presentinvention is illustrated in FIGS. 1B-1D. FIGS. 1B-1D illustrate a topview (FIG. 1B), a side view (FIG. 1C) and an isometric view (FIG. 1D) ofsystem 10.

In the present embodiments, system 10 comprises a tray 12 and aplurality of inkjet printing heads 16, each having a plurality ofseparated nozzles. Tray 12 can have a shape of a disk or it can beannular. Non-round shapes are also contemplated, provided they can berotated about a vertical axis.

Tray 12 and heads 16 are optionally and preferably mounted such as toallow a relative rotary motion between tray 12 and heads 16. This can beachieved by (i) configuring tray 12 to rotate about a vertical axis 14relative to heads 16, (ii) configuring heads 16 to rotate about verticalaxis 14 relative to tray 12, or (iii) configuring both tray 12 and heads16 to rotate about vertical axis 14 but at different rotation velocities(e.g., rotation at opposite direction). While the embodiments below aredescribed with a particular emphasis to configuration (i) wherein thetray is a rotary tray that is configured to rotate about vertical axis14 relative to heads 16, it is to be understood that the presentapplication contemplates also configurations (ii) and (iii). Any one ofthe embodiments described herein can be adjusted to be applicable to anyof configurations (ii) and (iii), and one of ordinary skills in the art,provided with the details described herein, would know how to make suchadjustment.

In the following description, a direction parallel to tray 12 andpointing outwardly from axis 14 is referred to as the radial directionr, a direction parallel to tray 12 and perpendicular to the radialdirection r is referred to herein as the azimuthal direction φ, and adirection perpendicular to tray 12 is referred to herein is the verticaldirection z.

The term “radial position,” as used herein, refers to a position on orabove tray 12 at a specific distance from axis 14. When the term is usedin connection to a printing head, the term refers to a position of thehead which is at specific distance from axis 14. When the term is usedin connection to a point on tray 12, the term corresponds to any pointthat belongs to a locus of points that is a circle whose radius is thespecific distance from axis 14 and whose center is at axis 14.

The term “azimuthal position,” as used herein, refers to a position onor above tray 12 at a specific azimuthal angle relative to apredetermined reference point. Thus, radial position refers to any pointthat belongs to a locus of points that is a straight line forming thespecific azimuthal angle relative to the reference point.

The term “vertical position,” as used herein, refers to a position overa plane that intersect the vertical axis 14 at a specific point.

Tray 12 serves as a supporting structure for three-dimensional printing.The working area on which one or objects are printed is typically, butnot necessarily, smaller than the total area of tray 12. In someembodiments of the present invention the working area is annular. Theworking area is shown at 26. In some embodiments of the presentinvention tray 12 rotates continuously in the same direction throughoutthe formation of object, and in some embodiments of the presentinvention tray reverses the direction of rotation at least once (e.g.,in an oscillatory manner) during the formation of the object. Tray 12 isoptionally and preferably removable. Removing tray 12 can be formaintenance of system 10, or, if desired, for replacing the tray beforeprinting a new object. In some embodiments of the present inventionsystem 10 is provided with one or more different replacement trays(e.g., a kit of replacement trays), wherein two or more trays aredesignated for different types of objects (e.g., different weights)different operation modes (e.g., different rotation speeds), etc. Thereplacement of tray 12 can be manual or automatic, as desired. Whenautomatic replacement is employed, system 10 comprises a trayreplacement device 36 configured for removing tray 12 from its positionbelow heads 16 and replacing it by a replacement tray (not shown). Inthe representative illustration of FIG. 1B tray replacement device 36 isillustrated as a drive 38 with a movable arm 40 configured to pull tray12, but other types of tray replacement devices are also contemplated.

Exemplified embodiments for the printing head 16 are illustrated inFIGS. 2A-2C. These embodiments can be employed for any of the AM systemsdescribed above, including, without limitation, system 110 and system10.

FIGS. 2A-2B illustrate a printing head 16 with one (FIG. 2A) and two(FIG. 2B) nozzle arrays 22. The nozzles in the array are preferablyaligned linearly, along a straight line. In embodiments in which aparticular printing head has two or more linear nozzle arrays, thenozzle arrays are optionally and preferably can be parallel to eachother.

When a system similar to system 110 is employed, all printing heads 16are optionally and preferably oriented along the indexing direction withtheir positions along the scanning direction being offset to oneanother.

When a system similar to system 10 is employed, all printing heads 16are optionally and preferably oriented radially (parallel to the radialdirection) with their azimuthal positions being offset to one another.Thus, in these embodiments, the nozzle arrays of different printingheads are not parallel to each other but are rather at an angle to eachother, which angle being approximately equal to the azimuthal offsetbetween the respective heads. For example, one head can be orientedradially and positioned at azimuthal position φ₁, and another head canbe oriented radially and positioned at azimuthal position φ₂. In thisexample, the azimuthal offset between the two heads is φ₁−φ₂, φ₂, andthe angle between the linear nozzle arrays of the two heads is alsoφ₁−φ₂.

In some embodiments, two or more printing heads can be assembled to ablock of printing heads, in which case the printing heads of the blockare typically parallel to each other. A block including several inkjetprinting heads 16 a, 16 b, 16 c is illustrated in FIG. 2C.

In some embodiments, system 10 comprises a support structure 30positioned below heads 16 such that tray 12 is between support structure30 and heads 16. Support structure 30 may serve for preventing orreducing vibrations of tray 12 that may occur while inkjet printingheads 16 operate. In configurations in which printing heads 16 rotateabout axis 14, support structure 30 preferably also rotates such thatsupport structure 30 is always directly below heads 16 (with tray 12between heads 16 and tray 12).

Tray 12 and/or printing heads 16 is optionally and preferably configuredto move along the vertical direction z, parallel to vertical axis 14 soas to vary the vertical distance between tray 12 and printing heads 16.In configurations in which the vertical distance is varied by movingtray 12 along the vertical direction, support structure 30 preferablyalso moves vertically together with tray 12. In configurations in whichthe vertical distance is varied by heads 16 along the verticaldirection, while maintaining the vertical position of tray 12 fixed,support structure 30 is also maintained at a fixed vertical position.

The vertical motion can be established by a vertical drive 28. Once alayer is completed, the vertical distance between tray 12 and heads 16can be increased (e.g., tray 12 is lowered relative to heads 16) by apredetermined vertical step, according to the desired thickness of thelayer subsequently to be printed. The procedure is repeated to form athree-dimensional object in a layerwise manner.

The operation of inkjet printing heads 16 and optionally and preferablyalso of one or more other components of system 10, e.g., the motion oftray 12, are controlled by a controller 20. The controller can has anelectronic circuit and a non-volatile memory medium readable by thecircuit, wherein the memory medium stores program instructions which,when read by the circuit, cause the circuit to perform controloperations as further detailed below.

Controller 20 can also communicate with a host computer 24 whichtransmits digital data pertaining to fabrication instructions based oncomputer object data, e.g., in a form of a Standard TessellationLanguage (STL) or a StereoLithography Contour (SLC) format, VirtualReality Modeling Language (VRML), Additive Manufacturing File (AMF)format, Drawing Exchange Format (DXF), Polygon File Format (PLY) or anyother format suitable for Computer-Aided Design (CAD). The object dataformats are typically structured according to a Cartesian system ofcoordinates. In these cases, computer 24 preferably executes a procedurefor transforming the coordinates of each slice in the computer objectdata from a Cartesian system of coordinates into a polar system ofcoordinates. Computer 24 optionally and preferably transmits thefabrication instructions in terms of the transformed system ofcoordinates. Alternatively, computer 24 can transmit the fabricationinstructions in terms of the original system of coordinates as providedby the computer object data, in which case the transformation ofcoordinates is executed by the circuit of controller 20.

The transformation of coordinates allows three-dimensional printing overa rotating tray. In conventional three-dimensional printing, theprinting heads reciprocally move above a stationary tray along straightlines. In such conventional systems, the printing resolution is the sameat any point over the tray, provided the dispensing rates of the headsare uniform. Unlike conventional three-dimensional printing, not all thenozzles of the head points cover the same distance over tray 12 duringat the same time. The transformation of coordinates is optionally andpreferably executed so as to ensure equal amounts of excess material atdifferent radial positions. Representative examples of coordinatetransformations according to some embodiments of the present inventionare provided in FIGS. 3A-3F, showing three slices of an object (eachslice corresponds to fabrication instructions of a different layer ofthe objects), where FIGS. 3A, 3C and 3E illustrate slices in a Cartesiansystem of coordinates and FIGS. 3B, 3D and 3F illustrate the same slicesfollowing an application of a transformation of coordinates procedure tothe respective slice.

Typically, controller 20 controls the voltage applied to the respectivecomponent of the system 10 based on the fabrication instructions andbased on the stored program instructions as described below.

Generally, controller 20 controls printing heads 16 to dispense, duringthe rotation of tray 12, droplets of building material in layers, suchas to print a three-dimensional object on tray 12.

System 10 optionally and preferably comprises one or more radiationsources 18, which can be, for example, an ultraviolet or visible orinfrared lamp, or other sources of electromagnetic radiation, orelectron beam source, depending on the modeling material being used.Radiation source can include any type of radiation emitting device,including, without limitation, light emitting diode (LED), digital lightprocessing (DLP) system, resistive lamp and the like. Radiation source18 serves for curing or solidifying the modeling material. In variousexemplary embodiments of the invention the operation of radiation source18 is controlled by controller 20 which may activate and deactivateradiation source 18 and may optionally also control the amount ofradiation generated by radiation source 18.

In some embodiments of the invention, system 10 further comprises one ormore leveling devices 32 which can be manufactured as a roller or ablade. Leveling device 32 serves to straighten the newly formed layerprior to the formation of the successive layer thereon. In someembodiments, leveling device 32 has the shape of a conical rollerpositioned such that its symmetry axis 34 is tilted relative to thesurface of tray 12 and its surface is parallel to the surface of thetray. This embodiment is illustrated in the side view of system 10 (FIG.1C).

The conical roller can have the shape of a cone or a conical frustum.

The opening angle of the conical roller is preferably selected such thatis a constant ratio between the radius of the cone at any location alongits axis 34 and the distance between that location and axis 14. Thisembodiment allows roller 32 to efficiently level the layers, since whilethe roller rotates, any point p on the surface of the roller has alinear velocity which is proportional (e.g., the same) to the linearvelocity of the tray at a point vertically beneath point p. In someembodiments, the roller has a shape of a conical frustum having a heighth, a radius R₁ at its closest distance from axis 14, and a radius R₂ atits farthest distance from axis 14, wherein the parameters h, R₁ and R₂satisfy the relation R₁/R₂=(R−h)/h and wherein R is the farthestdistance of the roller from axis 14 (for example, R can be the radius oftray 12).

The operation of leveling device 32 is optionally and preferablycontrolled by controller 20 which may activate and deactivate levelingdevice 32 and may optionally also control its position along a verticaldirection (parallel to axis 14) and/or a radial direction (parallel totray 12 and pointing toward or away from axis 14).

In some embodiments of the present invention printing heads 16 areconfigured to reciprocally move relative to tray along the radialdirection r. These embodiments are useful when the lengths of the nozzlearrays 22 of heads 16 are shorter than the width along the radialdirection of the working area 26 on tray 12. The motion of heads 16along the radial direction is optionally and preferably controlled bycontroller 20.

Some embodiments contemplate the fabrication of an object by dispensingdifferent materials from different dispensing heads. These embodimentsprovide, inter alia, the ability to select materials from a given numberof materials and define desired combinations of the selected materialsand their properties. According to the present embodiments, the spatiallocations of the deposition of each material with the layer is defined,either to effect occupation of different three-dimensional spatiallocations by different materials, or to effect occupation ofsubstantially the same three-dimensional location or adjacentthree-dimensional locations by two or more different materials so as toallow post deposition spatial combination of the materials within thelayer, thereby to form a composite material at the respective locationor locations.

Any post deposition combination or mix of modeling materials iscontemplated. For example, once a certain material is dispensed it maypreserve its original properties. However, when it is dispensedsimultaneously with another modeling material or other dispensedmaterials which are dispensed at the same or nearby locations, acomposite material having a different property or properties to thedispensed materials is formed.

The present embodiments thus enable the deposition of a broad range ofmaterial combinations, and the fabrication of an object which mayconsist of multiple different combinations of materials, in differentparts of the object, according to the properties desired to characterizeeach part of the object.

Further details on the principles and operations of an AM systemsuitable for the present embodiments are found in U.S. Pat. No.9,031,680, the contents of which are hereby incorporated by reference.

Reference is now made to FIG. 4, which is a simplified diagramillustrating the waste ink disposal sub-system of an additivemanufacturing apparatus according to the present embodiments. Asdiscussed above in respect of FIG. 1A, additive manufacturing apparatus114 further comprises one or more leveling devices such as a roller 326.Leveling device 326 serves to straighten, level and/or establish athickness of the newly formed layer prior to the formation of thesuccessive layer thereon. Leveling device 326 preferably comprises awaste collection device 136 for collecting the excess resin materialgenerated during leveling. Waste collection device 136 may comprise anymechanism that delivers the material to a waste tank or waste cartridge400. A waste ink curing device 402, which may be built into thecartridge 400, includes an energy source such as a light emitting diodeor one or more banks of light emitting diodes to cure the waste materialor waste ink 404 after being collected in the cartridge 400.

Reference is now made to FIG. 5, which shows in greater detail the wasteink collecting device 136. The device is connected to roller 326 whichmay have an internal pump and includes a reservoir 410 which collectsthe waste ink from the roller 326. The reservoir may additionallycollect waste ink from printing head servicing, such as periodic purgingof the print heads. A tubing system 412 collects ink from the reservoir410, typically using gravity to drain the waste ink from the reservoirinto a drainage or waste outlet pipe 414 into the cartridge 400. Adistribution head 416, having a shower head construction, distributesthe waste ink from showerhead inlets 418 via wicking channels, to drippoints 420 distributed evenly over the area of the collecting cartridge400. The idea is to dispense waste ink evenly over the collectingsurface of the cartridge, as will be explained in greater detail below.

Reference is now made to FIG. 6, which is a schematic view from above ofthe showerhead construction of the distribution head 416. Each of fourinlets 418 from waste pipe 414 leads to a series of wicking channels 422and then to 11 drip points or drip director outlets 420. The idea of thedrip points is to distribute the waste output evenly through thecartridge. The drip points are arranged as a distributed array for evendistribution of the waste ink over the floor of the waste collectingcartridge.

Reference is now made to FIGS. 7 and 8 which show successive stages inwaste ink 404 distributed over the floor of a cartridge 400. In FIG. 7distinct drops are apparent, but in FIG. 8 more ink has arrived and thedrops have coalesced. In the present embodiments, the drops are giventime to coalesce before carrying out curing. That is to say the curingenergy source is operated only after time has been allowed for the inkto be evenly distributed in the cartridge. The operation of the curingdevice may for example be set according to a flow rate of the waste ink.The faster the flow rate the sooner or more often curing is carried out.Failure to allow drops to coalesce before carrying out curing may leadto the formation of stalagmites, as discussed below.

Reference is now made to FIG. 9, which is a simplified diagram of thecartridge 400 showing the curing energy source as banks of mountings ofultra violet light emitting diodes (LED). The banks are set up toradiate evenly over the waste ink in the cartridge so that all of theink is cured and there are no shadows where puddles of liquid may beleft. In the present embodiment, three banks are provided. A first bank430 is located lengthwise along cartridge 400 towards one side. A secondbank is obscured by the shower head but is located lengthwise on asecond side of the cartridge opposite bank 430. Both banks are set at anoblique angle and a third bank 432 is located lengthwise in thedistribution head above the exit points. The third bank 432 carries outa curing operation when the cartridge 400 is full, to cure the ink leftin the distribution head 416, the undripped ink, so as to ensure that nohazardous liquid resin remains anywhere in the cartridge duringdisposal.

Reference is now made to FIG. 10, which is a simplified schematicdiagram that illustrates shielding 440 which may be located around eachof the drip points 420 at the bottom of the distribution head 416. Theshielding is provided to protect the drip points from curing energy fromthe LEDs. Cured ink at the drip points would otherwise block the drippoints or may lead to the formation of stalactites, as will be discussedin greater detail below. The shielding may protect against directirradiation and may also protect against reflected irradiation from mostdirections. Straight line specular reflection from the waste ink surfaceto the drip points cannot be protected against but the total energy insuch reflections is not sufficient to cause effective curing. That is tosay, direct vertical rays are minimal and are caused only by specularreflection off the ink at the bottom of the cartridge. As discussed, theLED banks are pointed at an oblique angle to the floor, thus preventingany direct reflection reaching the drip exit points.

The shielding may be in the form of hoods or cylindrical extensions thatsurround each drip point, extending downwardly. FIG. 11 shows cutawaydrawings of the wicking channels 422, the drip points 420 and theshielding 440.

Reference is now made to FIGS. 12A, 12B and 12C, which are a schematiclengthwise cross section of cartridge 400, a schematic widthwisecross-section of the cartridge and a schematic view from below of theshield array, respectively. FIG. 12A shows the shower head or drip array416 which is made of opaque plastic and the cartridge body wall 460which may be made of clear plastic. The shielding 440 is of opaqueplastic. In FIG. 12B it is seen that the drip points 420 are in factpointed terminations on which drips form and grow. A shovel 450 may beprovided below each drip point within the shielding to direct dripping.The drips fall onto the shovel and then exit via larger openings whichare less susceptible to clogging by stray UV light. In FIG. 12C the drippoints are shown with shielding around and shovels below each drippoint.

The drip director geometry is designed to avoid the formation ofstalactites at the drip points. Thus if drip points are exposed,stalactites may form from the drip directors. Drip director designswhich shield drops from UV exposure until they drop off of the dripdirectors do not exhibit this behaviour.

Reference is now made to FIGS. 13A and 13B, which are side schematicviews of a level detector 470 to detect whether cartridge 400 is full ornot. The level detector 470 comprises an emitter 472 and a detector 474,separated by an opaque spacer bar 476 and located outside transparentcartridge wall 460. In the example shown in FIG. 13A there are threesuch level sensors and in FIG. 13B the upper image shows that in theabsence of waste, light from the emitter is not reflected onto thedetector. In the lower image, waste material reflects the beam from theemitter so that it is picked up at the detector, and the cartridge isthus able to determine how full it is and when it needs to be changed.

A full cartridge is detected by the level detector 470 at the rear ofthe unit.

Upon detecting that the cartridge is full, printing is paused and theremaining waste is allowed to flow into the cartridge. A final pulse ofUV light is provided by the side mounted LED strips 430 to cure the lastof the waste in the main chamber of the cartridge. The 3^(rd) LED strip432, located on top of the Shower Head assembly (see FIG. 9) then curesany material remaining in the wicking channels.

The cartridge may now be safely removed and disposed of by the user, andafter installing a new waste cartridge, printing resumes.

Reference is now made to FIG. 14, which shows a variation of the leveldetector 470 in which prism 480 is moulded into transparent cartridgewall 460. The prism is designed with a refractive index that causestotal internal reflection when the cartridge is empty but fails toreflect when the cartridge is full. An advantage of the prism embodimentover that of FIGS. 13A and 13B is that the default position is thatlight is detected.

Reference is now made to FIG. 15, which illustrates a method for wasteink management during additive manufacturing. Manufacturing takes place490 and the waste ink is removed and collected 492. After collection thewaste ink is cured 494, and then removed 496 as a solid mass fordisposal.

Reference is now made to FIG. 16 which is a simplified flow chartillustrating a method of controlling the curing according to anembodiment of the present invention. The flow rate of the waste may bemonitored or estimated 500 and the curing may be carried out atintervals which are longer for lower flow rate and shorter for higherflow rate. In addition the curing energy source may be restricted tooperation when the ink drops have had enough time to be evenlydistributed, that is to say enough time for droplets to grow and merge.

Matching timing and dosage, meaning the amount of curing, to flow rate,prevents formation of stalagmites. If the dosage is too high stalagmitesform, since the resin does not have time to spread out before beingcured. On the other hand, if the dosage is too low, pools can form. Ifthe pools are too deep, the UV can cure a layer on top of the pool,trapping liquid resin underneath. If this happens, the trapped liquidcan never be cured because the cured layer on top of it blocks the UV.

A test was carried out using a peristaltic pump with a servo controller.Two eight watt UV LED light strips were used to carry out the curing andattached to a cycle timer. Timing was based on a maximum waste flow rateof 14 ml/minute, and a mixture of Objet VeroBlack resin with FC705support resin in a 50-50 mix (both of Stratasys Ltd., Israel).

Uncured resin may leak from pockets in the stored waste, making thewaste hazardous.

Reference is now made to FIG. 17, which shows five successive stages inthe build up of waste resin in the cartridge. It can be seen that theresin builds up in essentially flat layers.

FIG. 18 shows cured waste 210 removed from a cartridge. Edge 212 evincesevidence of layering.

Reference is now made to FIG. 19, which illustrates the formation ofstalagmites 220. Stalagmites form when the curing dosage is too high andthe waste is cured before it has a chance to spread out. Too low adosage leaves pools of uncured resin which become buried under curedresin and which thus cannot subsequently be cured.

Reference is now made to FIG. 20 which illustrates what happens when thedosage is too low. Waste resin is cut in two and pockets 230 are seen tohave formed. The pockets contain uncured resin which leaks into pool232.

Reference is now made to FIGS. 21A-21C. The existence of stalactites andstalagmites additionally cause shadowing, blocking the UV from certainareas and generally causing those areas to obtain too low a curing dose.The result is numerous pockets of uncured resin. FIG. 21A shows asection through a shadowed area, where many such pockets 240 can beseen. FIG. 21B shows pools 242 of uncured resin appearing behindstalagmites, and FIG. 21C by contrast shows a section through anunshadowed area, where good layering 244 is seen and there are no liquidpockets.

Reference is now made to FIG. 22 which uses triangles 250 to illustrateillumination patterns from lighting points 252 illustrated symbolicallyby yellow circles. Arrangement of the drip directors and LEDS so thatevery drip point receives direct radiation from both sides ensures, ifshadow causing features do form, no points are in full shadow from bothsides.

More generally, a combination of good drip director design, flow ratematched UV timing and LED/drip director arrangement can prevent theissues associated with shadows. Drip director design and UV timingprevent formation of stalactites and stalagmites and thus may prevent orreduce shadow formation. The design may also ensure that drip points atleast are irradiated from at least two sources, thus to mitigate theproblems when shadow-causing features do in fact form.

Reference is now made to FIG. 23, which shows an assembled view 260 ofone embodiment of the waste disposal system. As with the previousembodiments the system has certain functions including:

1) transporting waste resin and distributing the resin evenly in theWaste Cartridge;

2) curing the waste resin as it is generated; and

3) carrying out a final curing process after the cartridge is full toensure that all the waste ink is cured and thus chemically safe prior todisposal of the full cartridge.

Waste resin is generated in two locations, the service station whichruns head maintenance procedures and the roller. Waste from theselocations is transported to the waste curing system via a plumping setconsisting of tubes and fittings. Longer pipe 262 obtains waste from theroller and shorter pipe 264 obtains waste from the service station. Theplumbing set combines the waste resin streams coming from the roller andservice station at junction 266 between the two pipes and delivers thestreams to a single inlet of waste diverter 268—see exploded diagram onFIG. 24. This transport is motivated typically by gravity. However, insome embodiments of the invention, transport of the waste material inthe plumbing set may be controlled by one or more mechanical devicessuch as peristaltic pumps.

From this point on, even distribution of the waste material into thecontainer of the cartridge is handled by waste diverter 268 and showerhead 270 components. Referring to FIG. 25, waste diverter 268 splits thestream in to four equally spaced drip points 272, 274, 276 and 278.These drip points align with the four inlets of shower head 270 and thepassage to each drip point is of identical length. In the exampleillustrated the result is achieved by using looped channels to thenearer drip points 272 and 274 by contrast with straighter channels tothe more distant drip points 276 and 278. The fact that the distancesare the same helps to ensure that the hydraulic pressure is the same inall paths. The paths may be placed at the same height, again to ensurethat no path is preferential and the resin flow is as even as possible.

Large openings 280 allow for insertion of LED lamps for curing wastematerial remaining in shower head 270 and for sealing the wastecartridge before disposal in standard trashes. The distribution of thelamps is such as to ensure curing of all the remaining material presentin shower head 270 before disposal of the cartridge. Security openings282 are located above at least some of the drip points of shower head270 to help evacuating the waste material from waste diverter 268 incase of waste overflow.

Reference is now made to FIG. 26A which is a simplified view of showerhead 270. Shower head 270 matches with the four drip points of wastediverter 268 and divides each of the four streams into six new drippoints of a cross with diagonal pattern 284 to create twenty four drippoints in total. The twenty four drip points ensure even distribution ofthe resin in the cartridge as the shower head's drip points are evenlyspaced in the plan view of the cartridge. Thus the resin is evenlydeposited as it drops into the container portion of the waste cartridge.As the curing LEDs are only fired intermittently, the waste has time tofind its level and coalesce into a relatively even layer between curecycles. Transport through both waste diverter 268 and shower head iscaused by a combination of gravity and wicking. However, in someembodiments of the invention, transport of the waste material in thewaste diverter and/or the shower head may be controlled by one or moremechanical devices such as peristaltic pumps.

FIG. 26B shows a detail of the cross and diagonal pattern 284. Theshower head illustrates the use of corner radii to encourage ordiscourage wicking. Resin is specifically designed to wick into thesmall confines of print head firing chambers. This helps the print headsto prime and stay primed. Unsurprisingly, aggressive wicking behaviourfrom the resin occurs outside of the print head as well. As wickingaction happens best in tight corners with small or no radius, sharpcorners are implemented in places where we would like the resin to go orstay. Thus the shower head is provided with a sharp corner at the bottomof the inside of the flow channels where resin is intended to flow.Conversely, the outside walls of the flow channels have very large radiito discourage any wicking away from the flow channels.

Achieving an even distribution of material may provide consistent layerthicknesses and consequently good curing performance. In the wastecuring system of the present embodiments, flow into the single inlet issplit into twenty four separate streams by waste diverter 268 and showerhead 270 as discussed above. The design elements discussed may make surethe flow is split evenly amongst the twenty four drip points in showerhead 270.

Referring again to FIG. 24, side strips 290 hold several LED elements onone or more Printed Circuit Assemblies (PCAs) which carry out curing onthe resin inside the cartridge's container.

In a specific embodiment, the curing function is achieved through atleast two such UV LEDs-carrying side strips 290 placed onto polishedsheet metal reflectors 292 on each side of container 294. The reflectors292 may help diffuse the light from the LEDs inside the containerthereby improving the evenness of curing. Periodically, as the waste isbeing generated, the LEDs turn on for a cure cycle to cure the layer ofliquid waste that has accumulated on either the floor of the containeror on top of the cured resin in the container.

When a cartridge is full, a final curing step is done prior to disposingof the cartridge. As liquid resin is considered hazardous material, itis necessary to cure the residual resin that remains in the distributionchannels on the top of the Shower Head before the cartridge is disposedof. A third PCA with UV LEDs may be positioned above the shower head forthis purpose. When the waste cartridge is full, the LEDs on the thirdboard are fired. The firing of the third board may cure any remainingliquid resin in shower head 270. The final curing may also serve to sealthe holes in the top of the cartridge. As some water can leach out ofcured waste resin, such sealing is desirable. Once the final curing stephas been done, the cartridge is no longer usable as the drip points inthe shower head are sealed.

Reference is now made to FIGS. 27, 28 and 29, which show a detail of thewaste diverter 268 from three different angles respectively. Theincoming waste pipe causes waste to drip to central location 300 whereshield walls 302 keep the resin away from

UV holes 304. Wicking channels 306 in the surface serve as ducts todivide the resin flow for each of the four outlet directions and causethe dripping resin to start flowing into the four separate directions.

Waste drops into the central location 300, which serves as a smalltemporary reservoir at the inlet. The reservoir encourages the resin tospread out evenly to the entrances of all four diverter paths. Smallwicking channels 306 are formed into the bottom of the reservoir. These,again, aid in getting the resin to spread out across the entire surfaceof the reservoir. The channels are aimed at lower flow rates where,without them, there is some possibility that the resin could pool to oneside and begin wicking preferentially into one or other of the flowpaths rather than all of them. Once enough resin accumulates in thereservoir the resin level rises to meet the start of the flow paths. Theentrances to the flow paths also incorporate wicking features. Thepurpose of these is to ensure resin gets pulled into all four paths,again preventing preferential flow down one or two of the paths.

FIG. 30 is a schematic cross-sectional diagram of waste diverter 268,showing one inlet 310 dividing into four evenly spaced outlets 312, 314,316 and 318.

FIG. 31 is a schematic cross-sectional diagram showing waste diverter268 and the shower head 270 fitted together. As shown, the four outletsof the waste diverter fit with the four inlets of the shower head andfurther divide the flow to evenly spaced showerhead outlets 320.

Reference is now made to FIGS. 32, 33 and 34, which illustrate aconstruction of the nozzles of shower head 270 to prevent clogging ofthe nozzles due to unintended curing of resin dripping from the nozzle.By necessity, the bottoms of the drip points in both the waste diverterand the shower head need to be exposed to enable drops to fall. Thismakes them vulnerable to becoming clogged if stray UV light causes resinto cure on them. The shower head is part of the disposable cartridge andtherefore only needs to remain clogged for lifetime of a cartridgerather than the life of the product. However, the shower head issubjected to more frequent and larger doses of UV than the wastediverter, making protection of the Showerhead's drip points a challengeas well.

The drip points in both the waste diverter and shower head should thusbe protected from stray UV in order to prevent resin from curing whilestill in contact with them and thus sealing them off. This may beachieved through the incorporation of shield walls as discussed above,which may be arranged to form lamp shade structures 330 around dripnozzles 332. In waste diverter 268, lamp shade structures 330 may extenddown to the top of shower head 270 with only minimal clearance allowingfor the insertion and removal of the cartridge. In some embodiments,protection is preferably as complete as possible, as waste diverter 268is intended to last for the life of the printer.

Drip points 320 in shower head 270 also have lamp shades structures 330to minimize their exposure to UV, as can be seen in FIG. 31. There areseveral parameters to trade off in sizing lampshade structures 330. Thefirst parameter is the angle from the inside wall to the tip.Experimentally, it has been found that included angles 334 of below 50°(see FIG. 33) provide sufficient protection for the LED/reflector/drippoint arrangement of the present embodiments. The second parameter isthe inside diameter. If the inside diameter is too close to the drippoint, then resin can bridge the drip point and the inside wall of thelamp shade and may begin dripping from the lamp shade rather the dripdirector, resulting in stalactite formation. Another feature which helpsto prevent stalactite formation are the radii at the root of the droppoint and the lamp shade. Having large radii here discourages wicking ofthe resin from the drip point to the lamp shade. The final tradeoffparameter is height. The larger the diameter grows (desirable forstalactite prevention) and the smaller the included angle to the tip(desirable from a drip point protection perspective, the taller the lampshade needs to be. However, the taller the lamp shade is, the lessusable height there is in the cartridge. The challenge is to get thelamp shade diameter to the smallest one which will prevent stalactiteformation and the largest included angle that will prevent clogging inorder to maximize the usable volume in the Cartridge.

Reference is now made to FIG. 35 which illustrates stalactites 336forming on improperly shielded nozzles 338. The stalactites clog thenozzles and render the cartridge useless long before it is full.

Reference is now made to FIG. 36, which is a view from below ofshowerhead 270 with LED lamps 340 installed on either side of thecartridge. The figure illustrates an arrangement of LED lamps 340 aroundthe drip points of shower head 270 to provide curing which is as uniformas possible.

One of the challenges with the design of the waste curing system hasbeen ensuring even UV exposure even when stalactites/stalagmites form.Meeting this challenge requires special attention to the placement ofLEDs 340 and drip points 320 relative to one another. Drip points 320are arranged in eight slanted columns of three each. At the same time oneach UV LEDs-carrying side stripe 290 of the present embodiment thereare eight LEDs. The arrangement may ensure that the areas where everydrop lands have direct line of sight from three to four LEDs, so thatregions obtain

LED exposure even if stalactites/stalagmites form and occlude from oneor other direction. The arrangement of FIG. 36 has been effective atpreventing pools of uncured resin caused by shadows.

Reference is now made to FIG. 37, which illustrates a Virtual WastePipeline (VWP) model of the printing waste disposal process according toembodiments of the present invention. The VWP models the actual wastepipeline in the printer in order to calculate resin flows and UVexposure needs and timing.

UV dosage control presents several challenges: applying the appropriatedose for the material, timing the dose as the right amount of materialhas arrived in the cartridge, and not under or over-dosing. The VWPmodel helps overcoming these challenges. At a high level, the VWPenables tailoring dosage timing to account for different materials,varying volumes associated with different types of operations, and thetiming differences for transport of the waste to the cartridge, as wellas their combined effects. The virtual pipeline may be used tocompensate for the significant variety of conditions that the productwill encounter out in the field.

UV dosage has an effect on waste curing performance. There are a rangeof dosages that work well for a given condition (resin type(s), flowrate). Therefore, getting the dosage exactly right is not necessary.However, too much or too little UV exposure may cause issues asdiscussed hereinabove. Timing of the dosage is also relevant. If a toothick layer forms in the container between curing events then thematerial comprised in the lower portion of the layer will beunder-dosed. On the other hand, if the curing event happens too soon,then not all of the material may be in the container when the cure eventis executed; this can result in the layer thickness for the followingcure cycle being too high.

As mentioned above, overdosing of UV light can lead to stalagmiteformation and cause occultation and thus curing shadows (caused by thestalagmite structure). Underdosing of UV light can lead to hollowscomprising liquid resin that can no longer be cured. The doses neededfor different materials varies, and what may be underdosing for oneresin type may be overdosing for another resin type.

The VWP model is based on dosage units (DUs) which correspond to avolume of waste resin material multiplied by a cure factor, which isdirectly linked to the curing response of said resin material to the UVenergy. In case the waste resin is “pure” (composed of one single typeof resin), then a single cure factor is applied. On the other hand, ifthe waste resin is a “composite” material (comprises more than one typeof resin), then several cure factors are applied, each one to therespective volume of each collected resin material. Determining thevolume of waste for each specific resin material may be calculated onthe basis of the volume of resin used for printing the object until thewaste is collected (knowing the number of voxels printed with each resinmaterial) and the amount of waste material removed by the roller orduring print heads cleaning events. The DU model is applied at thedifferent inlets along the pipeline, so one can model the time it takesactual waste resin from different sources to reach the cartridge. Thereare generally three different waste generation events, one being thewaste material removed by the roller, and two other being generated bycleaning events of the print heads in the service station. Printing iscarried out using the print head and nozzles, and the roller passes overthe surface and mops, removing some 20% of the material and moregenerally between 10 and 30%. As a result the volume of the material toprint is obtained and it is possible to infer how much waste material isbeing produced. The estimate provides a guide as to the amount of curingenergy needed.

In some embodiments, waste material flows slowly through the pipes tothe cartridge. As mentioned above, gravity is the main feed factor, sothere is time between making the estimates and carrying out the curing.With gravity as the main feed factor the rate depends at any given timeon the amount of waste generated. The more waste generated the fasterthe waste resin is fed through the pipes. These complications mean thatthere is no one size fits all dosage that prevents under-dosing withhard to cure resins and over-dosing with easy to cure resins. The sameis true of timing of dosage timing. There is not a single timing betweencuring events or after servicing that will prevent over-curing andunder-curing the material in all situations. To address these issues,the VWP model of FIG. 37 may be used.

A dosage unit applies the resin material, again allowing estimates to bemade of the amount expected in the waste cartridge. The process ofcleaning the print head, also provides waste but in smaller amountsalthough again predictable.

It is possible to add one or more accumulators comprising a small tanknear the cleaning station and/or the roller, in order to (1) accumulatewaste material and (2) release said accumulated waste material when apre-determined volume threshold is reached. As the volume of wastematerial released by the accumulator is known, the amount of resinarriving at the cartridge and requiring curing is known with evengreater accuracy and appropriate curing energy (or DUs) may be applied.The accumulator(s) can be also used to introduce waste material into thepipeline at a predetermined rate. The rate limiting feature may be ofimportance when events producing a large volume of waste material occur(e.g. print head material emptying event at the cleaning station), andcontrol the volume of waste material entering the curing system. Thisalso allows a stricter control of DUs to be applied.

In the VWP model, the pipeline itself may be divided into cells. The DUsare added to the current DU total for that cell. At a configurableinterval, the cell contents all shift down to the next cell. At the endof the pipeline 356 the last cell's contents are added to the cartridgecell 358.

When enough resin has reached the cartridge, a cure cycle is initiated(applying a specific number of DU) and the resin in the cartridge cellis zeroed. The cycle continues throughout the printing process.

FIG. 37 illustrates resin accumulation 350 from the roller as well astwo resin waste sources 352 and 354 associated with the cleaningstation. Resin flows through pipe 356 at a steady rate so that the timeof arrival at cartridge cell 358 depends on the length of pipe that hasto be travelled. Delays can be entered in the calculation for each eventso that the curing energy can be timed for the arrival of the resin.

It is expected that during the life of a patent maturing from thisapplication many relevant additive manufacturing technologies will bedeveloped and the scope of the term “additive manufacture” is intendedto include all such new technologies a priori.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

The term “consisting of” means “including and limited to”.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment, and the abovedescription is to be construed as if this combination were explicitlywritten. Conversely, various features of the invention, which are, forbrevity, described in the context of a single embodiment, may also beprovided separately or in any suitable subcombination or as suitable inany other described embodiment of the invention, and the abovedescription is to be construed as if these separate embodiments wereexplicitly written. Certain features described in the context of variousembodiments are not to be considered essential features of thoseembodiments, unless the embodiment is inoperative without thoseelements.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting. In addition, any priority document(s) of this applicationis/are hereby incorporated herein by reference in its/their entirety.

What is claimed is:
 1. A cartridge for receiving waste ink from anadditive manufacturing device; the cartridge comprising a distributionhead, a curing source and a container, wherein the distribution headcomprises an inlet pipe and an array of drip points distributed oversaid cartridge, wherein said drip points are respectively surrounded byshielding to protect from direct irradiation from said curing source;and said curing source comprises a plurality of radiation locationsarranged around said container.
 2. The cartridge of claim 1, whereinsaid drip points comprise sharp terminations for droplet formation. 3.The cartridge of claim 1, further comprising drip-directing shovelsbelow each of said drip points and within said shielding.
 4. Thecartridge of claim 1, further comprising a second curing source withinsaid distribution head for curing ink remaining in said distributionhead when said cartridge is full.
 5. The cartridge of claim 1,comprising a level detector to detect filling of said cartridge.
 6. Thecartridge of claim 1, wherein said curing source comprises a bank oflight emitting diodes.
 7. The cartridge of claim 6, wherein said secondcuring source comprises a bank of light emitting diodes.
 8. Thecartridge of claim 1, wherein said curing source is located lengthwisealong said cartridge towards one side.
 9. The cartridge of claim 1,wherein said drip points comprise shielding against curing energy fromsaid source, to protect waste ink from being cured prior to drippingfrom said drip points.
 10. The cartridge according to claim 9, whereinsaid shielding comprises hoods surrounding each drip point.
 11. Thecartridge according to claim 1, further comprising a dispensing shovelbelow each drip point to direct dripping.